MAZATLAN UNIVALVES 353 
1695, 3 sp. curiously mended.—1696, 1 do. supporting 3 speci- 
mens of Ostrea conchaphila round its base. This, with several 
other specimens, retains its operculum. — 1697, 2 separate 
opercula. 
402. Moputus ————, sp. ind. 
Tablet 1698 contains a solitary and young shell resembling 
M. catenulatus in outline and tooth ; but with a well developed 
umbilicus, rounded and distinctly tuberculous keel, and whirls 
concave above. The colour is prettily mottled with purplish 
brown. It differs from M. disculus in the small tooth, conical 
spire and concave whirls. Long. °47, long. spir.°3, lat. *5, 
div. 80°. 
Hab.—Mazatlan ; 1 sp. with M. catenulatus ; L’pool Col. 
403. Mopuuus piscutus, Phil. 
Trochus disculus, Phil. in Kust. Mart. no. 308, p. 242, pl. 36, 
f. 14:—Zeit. f. Mal. 1846, p. 51, no. 19. 
Modulus disculus, H. & A. Ad. Gen. 1. 317. 
= Modulus duplicatus, var. A. Ad. in Mus. Cum. 
=Modulus dorsuosus, Gould, (ad fid. sp. typ.) Mex. & Cal. 
Shells, p. 10, pl. 14, f. 12. 
Comp. Monodonta modulus, Zam. in Kust. Mart. no. 307, 
p. 241, pl. 36, f. 11—13. (Hab.—W. Indies.) 
Known from M. catenulatus by the depressed spire, some- 
what rounded and strongly tuberculous keel, violet-tinted 
mouth, and very deeply cut tooth, with a broad groove on the 
base. The young specimens are imperforate, but the old ones 
have a small umbilicus. It most closely resembles one of the 
W. Indian species. Long. °6, long. spir. °32, lat. °65, div. 110°. 
Hab.—Mazatlan, Philippi—Do. ; 3 sp. with M. catenulatus ; 
P’pool Col.—** Found at Acapulco, Col. Jewett,” Gould. 
Tablet 1699 contains a young and an adult specimen. 
Genus FOSSARUS, <Adanson. 
Fossar, Gray, Syn. 1840:— Proce. Zool. Soc. 1847, p. 151, 
no. 206, (Forsar, err. typ.) 
pan si Phil. Arch. f. Nat.i. p. 42, 1841 :—Handb. Conch. 
p. 173. 
